[Soekris] Lightweight UPS

[Bob Camp]

Hi

A couple of simple "voting" diodes are a good idea, as is a fuse. If  
you are on line power you want the Soekris to run off of line power  
rather than the battery. You want no power going backwards into the  
regulated supply from either the battery or the Soekris. I know that  
one sounds odd, but I *have* burned up supplies that way (yes that's  
the plural).

Cutting the battery from the Soekris allows you to accurately charge  
the battery stack. In order to get a long life out of the batteries  
you don't want to put to much into it. Overcharge is the way most  
backup batteries die.

The next most likely way to kill a typical battery is to discharge it  
to deeply. Cutting the load off from the battery at a higher voltage  
reduces the amp hours available but significantly increases the life  
of the cell.

In most applications you are willing to trade off a shorter life on  
the battery for more capacity. Sad to say but many places trade  
shorter life for a cheaper charge setup as well.  The total cost of a  
very good charge setup for a small battery pack is less than $10 in  
parts.

Enjoy!

Bob


On Jul 4, 2007, at 2:49 PM, Joel Jaeggli wrote:

> Joel Jaeggli wrote:
>> Bill Maas wrote:
>>> Hi,
>>>
>>> here's a question that's been in my mind for a while now: is  
>>> there some
>>> widely available toy or other mass-produced item that happens to  
>>> have an
>>> excellent loader and batteries which can easily be ripped out and  
>>> could
>>> serve as a lightweight UPS for my 2 Soekris boxes? Must be able  
>>> to feed
>>> while loading of course. All available UPS systems seem to be in  
>>> the kW
>>> range. One of the reasons why I run these Soekris boxes is their  
>>> 3-10 W
>>> power consumption, so kW's are way out of range, as are the  
>>> prices of
>>> these things. [Links to] loader/feeder circuit diagrams also  
>>> welcome.
>>
>> 12 volt battery
>>
>> charge controller
>>
>> breaker
>
> The other thing I would observe is that if you put a regulated dc  
> power
> supply between the battery and the soekris you can put up with a
> multitude of sins that might otherwise be fairly messy depending on  
> the
> other components used.  obviously pulling your gel cells down to the
> point where they are flat is not such a great idea from a lifespan
> perspective but a 12volt 7ah battery should run a 5501 for about 10
> hours at a minimum unless you have lots of perhiperals.
>
>> all electronics corp is probably a good place to start... in fact:
>>
>> http://www.allelectronics.com/cgi-bin/item/BC-80/search/2_AMP_% 
>> 22#34;SMART%22#34;_BATTERY_CHARGER___MAINTAINER_.html
>>
>> looks promising
>>
>>> Bill
>>>
>>
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